1. Field of the Invention
The invention relates to a portable suction cleaner that is capable of operating from alternating current (AC) from a fixed power source or from direct current (DC) provided by an onboard battery.
2. Related Art
U.S. Pat. No. 4,835,409, issued May 30, 1989, to Bhagwat et al. discloses a corded or cordless dual mode power-operated vacuum cleaner that typical operates in the range of 3-48 volts DC. The AC input source current is converted to a relatively high DC current, chopped and used to charge the on-board batteries. The input voltage to the Bhagwat motor is constant regardless of the source of power. Bhagwat ""409, as well as other similar dual mode vacuum cleaners, presents a compromise between available power in a corded mode, and the duration of operation or battery life of the cordless mode. In many applications, it would be desirable to enjoy a longer battery life, and it would be acceptable to have a slightly lower suction power to achieve this extended battery life. On the other hand, there are instances where a higher suction power is necessary. It would thus be desirable to have that power available in a corded mode, utilizing the same portable suction cleaner.
In vacuum cleaners that are powered by a battery, the weight of the vacuum cleaner is often an important consideration to the customer. Reducing the weight of the vacuum cleaner, however, is often not possible without suffering from a corresponding decrease in the suction power of the vacuum cleaner. This is due to the fact that batteries having a higher voltage tend to weigh more than batteries having a lower voltage, all other considerations remaining equal. Manufacturers may therefore offer a range of models to their customers. Some of these models will weigh more, but will incorporate higher power motors and therefore better suction. Others of the models will weigh less but will suffer from reduced suction. In offering such different models to customers in the past, it has been necessary to manufacture different control circuitry for each of the different models. This can add significant cost to the manufacturing and assembly of the different vacuum cleaners.
According to one aspect of the invention, a power supply is provided for supplying power to a vacuum cleaner. The power supply includes a first and second AC input terminal, a first and second DC input terminal, a switch, and a control circuit. The switch selectively couples either the AC or DC input terminals to a motor. The control circuit monitors the voltage at the first and second DC input terminals when the switch has electrically coupled the first and second DC input terminals to the motor. The control circuit terminates power to the motor when the voltage between the first and second DC input terminals falls beneath a threshold level.
According to another aspect of the invention, a method is provided for controlling the power to a vacuum cleaner motor. The method comprises providing an AC and a DC input, along with providing a switch that alternately electrically couples the AC or DC input to the motor. The method further includes detecting the voltage at the DC input when the DC input is electrically coupled to the motor, comparing the voltage at the DC input to a predetermined threshold level, and terminating the electrical coupling of the DC input to the motor when the DC input falls below the predetermined threshold level.
According to yet another aspect of the present invention, a vacuum cleaner is provided that includes a housing having an intake, and impeller, and a motor for operating the impeller. A battery input is provided for receiving power from a battery, and an AC input is provided for receiving power from an AC power outlet. A switch couples either the battery input or the AC input to a motor. A controller monitors the voltage level at the battery input when the switch is coupled with the battery input to the motor. The controller decouples the battery input from the motor when the voltage level at the battery input falls below a predetermined threshold level.
According to yet another aspect of the present invention, a circuit board for controlling a vacuum cleaner is provided. The circuit board includes a battery input, a motor terminal, a controller, and at least one electrical junction on the circuit board. The controller selectively supplies power from the battery input to the motor terminal when the battery input has a voltage that exceeds a predetermined threshold value. The controller decouples the battery input from the motor terminal when the battery input voltage falls below the predetermined threshold value. The electrical junction sets the predetermined threshold level at a first value when the junction is closed, and sets the predetermined threshold level at a second value when the electrical junction is open.
A portable corded/cordless suction cleaner according to one embodiment of the inventor has a direct current (DC) motor adapted to operate at two different DC voltages. The suction cleaner has an AC input power cord and also has on board DC batteries. A circuit is connected to the AC power cord, to the batteries and to the DC motor. The circuit converts 120 volts AC to a voltage suitable for the motor in a corded mode when 120 volts AC power is selectively supplied to the circuit and selectively applies that voltage to the DC motor. The circuit selectively applies the voltage from the batteries to the motor in a cordless mode. The circuit further has a manually operated switch for selection of the corded or cordless mode. The circuit detects when the voltage in the batteries has fallen below a threshold and cuts off power to the motor if such a voltage drop has occurred. This increases battery longevity. The suction cleaner has the advantage of extended battery life while in the cordless mode, while still providing a higher level of suction power while operating in the corded mode.
The present invention provides the advantage of having a single controller which accommodates either an AC input or a DC, battery input. When the battery level drops, the controller shuts down the motor indicating that it is time for the battery to be either replaced or recharged. By shutting down the batteries prior to their full depletion, the number of times which the battery can be recharged is increased. The present invention also allows a single controller to accommodate at least two batteries of different voltages. A single controller can therefore be manufactured to accommodate vacuum cleaners having two different types of batteries. This helps reduce the costs associated with manufacturing the vacuum cleaner. Other objects, features, and advantages of the invention will be apparent from the ensuing description in conjunction with the accompanying drawings.